In general, an unmanned aerial vehicle, which is also called a “drone”, is an unmanned flight vehicle which is in the form of a helicopter and flies without a human pilot aboard while being guided by wireless radio waves, and the unmanned aerial vehicle has been initially developed for military purpose, but recently, the unmanned aerial vehicle is used for various purposes such as high-altitude aerial photographing and delivery.
As illustrated in FIG. 1, the unmanned aerial vehicle includes a main body unit 10 which is equipped with a main board or the like for controlling a flight operation, a plurality of motors 20 of which the rotational speed is adjusted by the main board, support frames 30 which radially diverge from the main body unit 10 in order to support the plurality of motors 20, and propellers 40 which are coupled to rotating shafts of the plurality of motors 20, respectively, and output thrust.
For example, the plurality of support frames 30 may include first, second, third, and fourth support frames 31, 32, 33, and 34 which are provided at intervals along a circumference of the main body unit 10, the plurality of motors 20 may include first, second, third, and fourth motors 21, 22, 23, and 24 which are provided at end portions of the first, second, third, and fourth support frames 31, 32, 33, and 34, respectively, and the plurality of propellers 40 may include first, second, third, and fourth propellers 41, 42, 43, and 44 which are coupled to rotating shafts of the first, second, third, and fourth motors 21, 22, 23, and 24, respectively.
Hereinafter, an operation of the unmanned aerial vehicle in the related art will be described with reference to FIGS. 1 and 2.
FIG. 2 is a view illustrating a principle of the position movement of the unmanned aerial vehicle in the related art.
First, the position movement of the unmanned aerial vehicle in a state in which the unmanned aerial vehicle is in the air will be described. As illustrated in FIG. 2, thrust (denoted by 53) of the third propeller 43 generated by the third motor 23 is adjusted to be higher than thrust (denoted by 51) of the first propeller 41 generated by the first motor 21, such that the posture of the unmanned aerial vehicle is tilted downward (denoted by 60, leftward in FIG. 2) toward the first motor, and the position of the unmanned aerial vehicle is translationally moved (denoted by 70).
In addition, how to maintain the horizontal posture of the unmanned aerial vehicle in the state in which the unmanned aerial vehicle is in the air will be described. As illustrated in FIG. 1, the horizontal posture of the unmanned aerial vehicle may be maintained by decreasing the rotational speed when the unmanned aerial vehicle descends and by increasing the rotational speed when the unmanned aerial vehicle ascends while equally adjusting the rotational speeds of the motors 20.
However, the unmanned aerial vehicle in the related art has the following problems.
There is a problem in that additional undesired rotational motion (pitching, denoted by “60” in FIG. 2) occurs inevitably when the unmanned aerial vehicle translationally moves (denoted by “70” in FIG. 2). For example, there is a problem in that in a case in which distances and heights between the unmanned aerial vehicles positioned in a front and rear direction, an up and down direction, or a left and right direction are adjusted during a group flight when a number of unmanned aerial vehicles fly, there is a risk of collision due to the rotational motion (denoted by 60), a long period of time is required for docking and there is a risk of collision due to the rotational motion (denoted by 60) when allowing the unmanned aerial vehicle to dock with another unmanned aerial vehicle in the air, or it is difficult to precisely operate the unmanned aerial vehicle and operation time is increased due to the rotational motion (denoted by 60) caused by the position movement when performing various tasks or operations between the air and the ground such as aerial photographing.
In addition, there is a problem in that because the posture of the unmanned aerial vehicle is maintained only by controlling the rotational speeds of the motor 20, the posture of the unmanned aerial vehicle cannot return to the original posture when disturbance occurs, that is, when external force is applied.